In many industrial applications wherein fluids are transported from one location to another pipelines are used. A continuing problem with such pipelines is that corrosion can occur in many forms and can weaken the pipeline to a point of failure. One of the most common types of corrosion is corrosion from the inside of the pipe as a result of corrosive materials which are transported in the pipe either as the primary material transported or as a contaminant material. This corrosion in many instances tends to form pits in the pipe and eventually may result in pinhole leaks or larger failures if the corrosion is particularly severe before discovery. Such failures typically result primarily in the loss of transported material with the resulting contamination of the environment and the like.
Frequently such pipelines are covered with coating materials, which may also function as an insulation material. Such coatings may be organic or inorganic fibrous materials, polymeric foams and the like. When such materials are used to cover the outside of the pipe, the potential exists for the accumulation of water in the coating material, particularly in pipelines which are insulated using insulating materials which are contained in an outer shell. Such materials are frequently used with an outer shell to protect the insulating material from the weather. When water collects in such insulating materials and comes in contact with the outer surface of the pipe, which is typically carbon steel, the water becomes corrosive to the pipe. Corrosion to the pipe in this fashion results in corrosion of the pipe from the outside over relatively large areas and may result in catastrophic pipe failures when periods of increased pressure occur and the like. Since many such insulating materials are closed cell or otherwise retain water, it is not feasible to remove this water by simply placing drains in the bottom of the outer shell. Further, the insulating material may be formed with an integral outer shell of sealing polymeric material or the like. Alternatively, the outer shell may be formed of a thin metallic material such as galvanized sheet steel. In any event, pipe failures for this reason are a significant problem in industry. Such pipes are frequently used in oil production operations, refinery operations, chemical operations, and a wide variety of other applications where it is desirable to transport fluids, especially if the fluids are at a temperature other than ambient.
As a result of the large number of pipe failures from external pipe corrosion as a result of water present in coating materials, methods have been sought to eliminate such failures.